In the practical application of the Ethernet network, various protection technologies are widely utilized to realize the redundancy backup between a main path and an alternate path. When both of the main path and alternate path are in good condition, the protection data forwarding function of the alternate path is blocked, and the protection data among networks are transmitted on the main path; when the main path is out of order, the protection data forwarding function of the alternative path is unblocked, and the protection data among the network are transmitted on the alternate path, so as to avoid the protection data being received repeatedly and forming the broadcast storm in the normal state of the network; when the main path of the network is out of order, the alternate path is invoked to transmit the protection data in order to improve the anti-fault capability of the Ethernet, and to satisfy the high real time requirement that convergence time should be less than 50 ms when the handover is performed.
Taking the Ethernet multi-rings protection technology for example, as shown in FIG. 1a, nodes S1 to S6 are Ethernet switches, and Network B is connected with node S2, Network A is connected with node S5. A communication process is performed between Network A and Network B. There are four physical paths between Network A and Network B, viz. Network A<->node S5<->node S3<->node S2<->Network B, Network A<->node S5<->node S3<->node S4<->node S1<->node S2<->Network B, Network A<->node S5<->node S6<->node S4<->node S3<->node S2<->Network B, Network A<->node S5<->node S6<->node S4<->node S1<->node S2<->Network B.
When the Ethernet multi-ring protection technology is applied, a ring and a sub-ring are adopted generally. The ring is a whole Ethernet ring, and the sub-ring is an Ethernet ring connected with another ring or network through an interconnection node. The interconnection node, which is also called as a shared node, is a public node belonging to two or more Ethernet rings at the same time.
As shown in FIG. 2a, it includes a ring and a sub-ring, and the Ring 1 is a ring, Ring 2 is a sub-ring. Ring 1 includes nodes as below: S1, S2, S3, and S4, and includes links as below: <S1, S2>, <S2, S3>, <S3, S4>, and <S4, S1>. Ring 2 includes nodes as below: S3, S5, S6, and S4, and includes links as below: <S3, S5>, <S5, S6>, and <S6, S4>. It should be specially noted that link <S3, S4> belongs to Ring 1 but not Ring 2. In the above, node S3 and node S4 are interconnection nodes of Ring 1 and Ring 2, Port 33 of node S3 and Port 43 of node S4 belongs to Ring 2, which are called as access port.
In the ring network, when the ring network is in good condition, a link in a ring should be in a blocked status for forwarding the data message to prevent forming a ring, wherein the link is called as ring protection link (or always blocked link etc.); by the ring protection link, it is involved in the performing of the handover between the main path and alternate path in a ring. The node having a ring protection link is called as ring protection link control node herein. As shown in FIG. 2b, in Ring 1, node S4 is a ring protection link control node, and the link directly connected with Port 41 of node S4 is the ring protection link of Ring 1. In Ring 2, node S5 is a ring protection link control node, and the link directly connected with Port 52 of node S5 is the ring protection link of Ring 2. In normal situation, the ring protection link control node of Ring 1 and Ring 2 blocks the data forwarding function of their secondary ports, to avoid the protection data being forwarding repeatedly and forming a broadcast storm.
When the links of Ethernet ring network is in good condition, the ring protection link control nodes of the ring and the sub-ring block the protection data forwarding function of the secondary ports. As shown in FIG. 2a, node S4 blocks the protection data forwarding function of Port 41, node S5 blocks the protection data forwarding function of Port 52, and the communication path between network B and network A is: Network B<->node S2<->node S3<->node S5<->Network A.
When the link of the Ethernet multi-ring network has a fault, if the fault link is not a protection link, the ring protection link control node unblocks the protection data forwarding function of the secondary port, each node updates its address forwarding table respectively and the transmission of communication among the networks is according to the new path. As shown in FIG. 2b, the link S2, S3 of Ring 1 has a fault; when detecting the link fault, the node S2 and node S3 block the data forwarding function of port 22 and port 31 respectively, and inform other nodes that the link has a fault. After receiving the fault notification, node S4 (the ring protection link control node) unblocks the protection data forwarding function of port 41, and each node on Ring 1 will update the address forwarding table. The new communication path between Network B and Network A is: Network B<->node S2<->node S1<->node S4<->node S3<->node S5<->Network A.
When the link of the Ethernet multi-ring network is recovered, a recovery handover is performed, and the network transmission resumes the transmission path in the normal state. Due to the path change, their nodes need to update the address forwarding tables.
In addition, if the nodes of the sub-ring update their address, but the nodes of the ring do not update their address, some problems as below may occur.
For example, in FIG. 2c, When the Ethernet multi-ring network is in good condition, the communication path between network B and network A is: Network B<->node S2<->node S3<->node S5<->Network A. When the link of the sub-ring Ring 2 has a fault, e.g., the link <S3,S5> has a fault as shown in FIG. 2c, after detecting the link corresponding to ports 51 has a fault, node S5 updates its address forwarding table, blocks the protection data forwarding function of Port 51, unblocks the protection data forwarding function and sends fault status frame outwardly. After receiving the fault status frame, node S6 updates the address forwarding table, and a new communication path between network A and Network B is formed. After node S5 and node S6 update the table forwarding table, the protection data sent from Network A to Network B can arrive at Network B through the broadcast of node S5 and node S6, and meanwhile, each node learns the address of Network A. But before Network A sends data to network B, if Network B sends data to Network A, a lot of packages may be lost; the reasons of the above is as follows: the node S2 hasn't updated the address forwarding table; there are still the items before the path handover in the address forwarding table, i.e. the wrong address item; the protection data sent from Network B to Network A is still forwarded according to the wrong address forwarding table, i.e., the data is sent from the output port 22 of node S2, and actually, these data will not arrive at Network A because of link fault and port blocking; as long as the switch learns the correct address output port of Network A, the data can arrive at Network B. Thus, the path handover time sent from Network B to Network A depends on whether there is traffic from Network A to Network B, and the time is always beyond 50 ms. When the Ethernet ring path performs a recovered protection handover, the communication between Network A and Network B also has the similar problem.
From the above analysis, it can be seen that when a link of a sub-ring has a fault, the sub-ring needs to inform nodes in the ring to update the address forwarding table by sending a protocol frame to the ring via the interconnection node. Therefore, it is very significant to provide a method that the interconnection node selective sends an address updating notification frame of a sub-ring to the ring.